It’s perfectly obvious why an aging poet, a Jewish barber and the king of Germany fall in love with Louise Maske, a young Düsseldorf housewife married to a stodgy government clerk — and it’s not because her bloomers fell off while she was watching a parade.

Erin Spears portrays this central character in Steve Martin’s “The Underpants,” the opening production of the seventh Artists’ Ensemble Theater season, and she is absolutely enchanting. Her mobile face expresses innocence and wonder and concern and delight and more with a vivacity that makes the ridiculous premise of this adapted German stage piece almost completely believable.

Her husband, Theo, brusquely executed by Stephen F. Vrtol III, has long since decided how wives — even those as attractive as his own — should behave, and he pompously pronounces his predilections to all, whether they want to listen or not.

Theo also hides another predilection — which he unveils to Gertrude Deuter, the upstairs tenant lustily portrayed by Margaret Raether — that is a bit predictable but still hilarious. Gertrude exults vicariously in the delights she wishes for the lovely Louise and connives with her to make them come true.

And then there are the renters, both drawn by their view of Louise’s “accident” at the royal parade. Will Clinger pushes the poet Frank Versati, in his opera cape and feathered hat, right up to the top but manages to keep him from sliding over. David A. Gingerich, as the barber driven by jealousy, displays a  range of physical humor that approaches the incredible.

John Chase is a third would-be roomer, one who did not observe Louise’s public shame, whose timidity is as extreme as the temerity of his counterparts. He’s silly, but he’s fun.

Last but not least is Michael Palmenderi as the unexpected visitor, a fun fillip at the conclusion of this morality tale.

Director Richard Raether keeps the play moving at an excellent pace, working the Martinesque humor very effectively and eliciting a solid ensemble performance from the cast. The off-kilter aspects of the script get a boost from the off-kilter set design by Angelo O’Dierno, and Genny Bonavia’s costumes add to the flavor.

This is not a production for kids because of some rather ribald situations, and it does require a willingness to listen and enjoy the situation as much as the lines — but it offers laughs throughout. “The Underpants” runs through Sept. 26 in Cheek Theatre of Clark Arts Center on the Rockford College campus. Call 815-904-2277 for ticket information.

Victor R. Yehling has been reviewing, directing and performing in plays in Rockford and elsewhere for more than 45 years. He holds a degree in theater from Beloit College.